Selective signal circuits



Aug. l2, 1952 G, R CLARK SELECTIVE SIGNAL CIRCUITS Filed Aug. 17, 194e N QN s p I mv .fm Mv H HQN kwh #l vw) mw 1N VEN TOR. G/z 5f/P7 AP. cnw/f ATTORNEY Il-; L+

v EN Il.. I ll M1 b@ v v MJ NWI n Patented Aug. 12, 1952 UNITED STATES PATENT OFFICE SELECTIV E SIGNAL CIRCUITS Gilbert R. Clark, Nutley, N. J., assigner to'ledel'al Telephone and Radio Corporation,l New York,- N. Y., a corporation of Delaware Application Angustl'i, 1946, Serial No. 691,283

(Cl. Z50-27)' 1 Claim. l

Thisinvention relates to selective signal operative-circuits and more particularly to circuits providing selective relay operation in response tothe exceeding ofa predetermined ratio be- Innen two signals.

In a. copending application of J. A. Herbst andaapplicant, Serial No. 691,282, led August 17, 1946, now Patent No. 2,523,300, a printer telegraph circuit is illustrated provided with a receiving circuit which has therein means for segregating marking and spacing signals for selective operation of a printing telegraph relay system. The present application describes and claims in moreparticularity the-signal selector circuit which may, for example, be used in printer telegraph systems,

It is an object of my invention to provide a selective control system which will providefor selective operationinwresponseto differences of two or more signals.

It is another object of myv invention to provide a signal selective circuit wherein'two signals are separated and rectiiied, the rectified voltages being applied in opposite polarity'to an electron discharge device sothat the device will operate selectively in responseto a difference in the signais.

It is a further object'of myinvention to provide a system `responsive rto received signals of different frequencies which will be very sensitive to small differences in amplitude and will produce control voltages substantially independent of variations of amplitude difference beyond a predetermined level.

According to a. feature of my invention, I may provide means such as filters for separating two signals. These separated signals may be rectified and applied differentially to the grid of an electron discharge device. When one of these voltages, preferably the positive voltage, exceeds the negative voltage applied to the grid, this tube is designed to operate to pass signals. In the output of this electron discharge device is provided another current limiting device which preferably is also an electron discharge means. This second electron discharge means is so biased, that of the signals passed by the first,

only that portion below a predetermined amplitude will be further passed on. This signal then, in the output of the second electron discharge means, will have an output pulse duration substantially equal to the time at which the positively applied voltages exceed the predetermined level of the negatively applied voltages and of an amplitude determined by the second 2 electron discharge device. These outputpulses may then be-applied through a. third electron discharge device so biased that upon application of these pulsos, the output energy will be greatly increased. The output energy of this third tube may be taken across a low impedance means, such asa. cathode follower for example, and applied to a relay operating distributor means. or to 'other means for controllinga relay operationl While I have-outlined above-the general objects and features of my invention, a better understanding vthereof and further r objectsA and features will be had from the particular description of an embodiment thereof made with reference to the accompanying drawing, the single figure of which is a .schematic circuit diagram partly in block form illustrating an example of a circuit' in accordance with my invention.

Turning to thek figure, reference character I represents a signal` source whichv preferably contains components of two different signals. These different signals may be, for example, different frequencies, for example, source I may constitute a. radio receiver of the type disclosed inthecopending application Serial No. 691,282, referred to above. The output signal. from I may be applied over line 2 to the signal filters 3 and 4' respectively, which serve to segregate thedifferent frequency signals. It is clear thatv if de-v sired, other types of segregatingnetworks for different types of signals may be'used in place of such filters. The output energy from filter 3 may be applied over coupling network 5 to a rectier 6. Similarly, the output from filter 4 may be applied over coupling network 1 to a rectifier 8 coupled in opposite polarity to rectier 6. The output of rectifiers B and 8 may then be applied over potential dividing resistors 9 and III and a coupling network II, which may serve to smooth out the rectified energy, to the grid of an electron discharge device I2. Electron discharge device I2 is preferably so biased that it will respond to the predominance of the positive voltage over the negative voltage to produce output in the plate circuit of this tube. With such a system, it is clear, however, that the output energy passed will vary in amplitude in accordance with the amplitude of the different signals. For best operation, however, it is desirable that the energy be limited to a predetermined maximum value. Accordingly. a second electron discharge device I3 is provided coupled to the output of electron discharge device I2. 'I'his second electron discharge device is so biased that in the absence of operation of dis- This tube in conjunction with electron discharge device I3 serves as a D. C. limiter producing output energy at a constant 10W amplitude potential if the resultant voltage on the grid of tube I2 is even slightly negative'and proresultant on the grid of tube I2 is even slightly positive. Accordingly, the output of electron discharge tube I3 effectively produces a regeneration of pulse input signal in accordance to which of the lter outputs is stronger regardless of the absolute magnitude of the energy applied thereto. l

The output energy from the tube I3 is coupled over voltage dividing resistors I4, I5 to the input grid of a third tube I6, Tube I-B is sobiased that when low voltages appear in the output of tube I3 only a small operating energy will be produced in this tube while, upon application o-f positive pulses to tube I2 and consequent increase tov a 'higher amplitude, the output energy from tube I6 may be produced |at a higher value also substantially constant. The output energy from tube I6 may be taken out over a cathode follower resistor I'I over line I8 and applied to a relay operating distributing means I9 or other relay control circuits.

It will be evident that many changes in the circuit as described herein may readily occur, to those skilled in the art. The specific example herein given is made merely by way of example and is not considered as a'limitation on the scope of my invention.

I claim:

'A'selective control apparatus for a telegraph` system comprising an input circuit, a pair ofV selector circuits each responsive to a signal of a diierent frequency, a first rectifier coupled across` one. of said selecto-r circuits so` as to produce a positive output in response to a signal of a' first frequency, a iirst load resistor shunted Vducing a constant high positive potential if the Y across said first rectifier. a second rectier cou'- pled across the other of said selector circuits so as to produce a negative output in response to 'a signal of a second frequency, a second load resistor shunted across said second rectifier, a potential dividing resistance network serially connected between the outputs of said rectiers, a rst grid controlled vacuum .tube normally biased to be conductive upon receipt of a positive voltage upon the grid thereof, a resistancelcapacity iilter network serially disposed between the substantial midpoint of said potential dividing resistance and the grid of said tube, a

second grid controlled vacuum tube coupled to the output of said first tube said second tube normally biased to pass a small current in one operating condition of said rst tube, corresponding to the predominance of positive output of said rst rectier and to pass a larger current4 of predetermined magnitude in a second operating condition of said firstA tube, corresponding to the predominance of negative out.- put of said second rectifier, load means responsive to the output of said selector circuits,y an` amplifier coupled between the output of said.

second tube and said load means, to energize said means in accordance with thesignal frequencies applied to said rectiers. Y

GILBERT R. CLARK.

REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS 

